Such a refrigerating system is known from U.S. Pat. No. 4,267,702 entitled "Refrigeration System With Refrigerant Flow Controlling Valve" and issued May 19, 1981.
It is known that if during the off-periods of the compressor the condenser is not shut off from the evaporator, which gives rise to pressure equalization between the condenser and the evaporator, this produces energy losses in the refrigerating system. These losses arise because the pressurized liquid from the condenser expands via the expansion means, the gas thus formed being condensed in the evaporator, resulting in a thermal input in the evaporator.
In accordance with U.S. Pat. No. 4,267,702 a valve is arranged between the condenser and the evaporator and comprises a pressure-sensitive diaphragm, the pressure at one side of the diaphragm being equal to the condenser pressure and the pressure at the other side being the condenser pressure reduced by means of a restriction. The diaphragm is responsive to the pressure difference to open and close the passage between the condenser and the evaporator when the compressor is turned on and off respectively. During the on-period of the compressor the chambers at opposite sides of the diaphragm will be entirely filled with liquid. After the compressor has been turned off a pressure difference arises across the diaphragm, which difference depends on the size (passage) of the restriction and on the sensitivity of the diaphragm. A requirement for the correct operation of this system is that the restriction should be very small (of the order of 0.01 mm). However, the disadvantage of such a small passage is that the likelihood of soiling and hence clogging is substantial. If a larger passage is selected for the restriction the diaphragm construction will have to be very sensitive, large and hence expensive.
It is also known to arrange an electromagnetic valve between the condenser and the evaporator in such a refrigerating system, which valve is responsive to the compressor being turned on and off. Such a valve consumes additional power. This is advantageous only in large refrigerating systems because the gain in power as a result of shutting off the refrigerant flow between the condenser and the evaporator during the off period of the compressor is then comparatively high. In a small refrigerating system, such as a domestic refrigerator, an electromagnetic valve consumes so much power that this gain in power is substantially cancelled.
Further, U.S. Pat. No. 2,331,264, entitled "Refrigeration System" and issued Oct. 5, 1943, describes a refrigerating system comprising a rotary compressor and a valve arranged between the capillary and the evaporator. During the on-period of the compressor one side of the diaphragm of the valve is at the evaporator inlet pressure and the other side is at the evaporator outlet pressure via a capillary line. After the compressor has been turned off the evaporator outlet line is shut off by a non-return valve and the capillary line and hence said other side of the diaphragm will be at the higher condenser inlet pressure, causing the valve to close the passage to the evaporator. This system employs a rotary compressor and therefore an additional non-return valve is needed in order to prevent the evaporator pressure from becoming too high. Moreover, it is common practice to arrange a bypass comprising an electromagnetic valve across the rotary compressor between the condenser and the capillary line. If such a system utilizes a reciprocating compressor such a bypass comprising an electronagnetic valve is indispensable.